On Wed, Sep 24, 2008 at 10:53:36AM -0400, Kell, Scott wrote: > > I then saw the post on the USRP filter response by Firas [1] where he > > showed that for an overall decimation rate of 64 the CIC filter > response > > had better than a 55 dB anti-alias rejection. [2] But I'm seeing only > 42 > > dB (overall response). > > > > Does anyone have any ideas that explain this 13 dB discrepancy in the > > filter response? Or am I missing something obvious... > > > > [1] http://lists.gnu.org/archive/html/discuss-gnuradio/2007- > > 05/msg00191.html > > [2] http://www.nabble.com/file/8500/%280%20- > > > %2032%29MHz%29%20CIC%20Frequency%20Response%20%28CIC%20decimation%20%3D3 > 2% > > 29.JPG > > [Kell, Scott] > To illustrate what I'm talking about, I set the USRP as follows: > Data rate: 500 kSamples/sec, > Center frequency: 1250 kHz > > I put a 9dBm tone in at 50 kHz and measured the largest alias in my > "passband".
What daughterboard are you using? If it's the Basic Rx, it's spec'd from 1 MHz to 250 MHz. There's a transformer on the board that limits the bottom end. See the datasheet http://www.ettus.com/downloads/er_ds_txrx_dbrds_v4.pdf Eric _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
